In Vitro Formation and Characterization of the Skeletal Muscle α·β Tropomyosin Heterodimers

Kalyva, Athanasia and Schmidtmann, Anja and Geeves, Michael A.
(2012)
In Vitro Formation and Characterization of the Skeletal Muscle α·β Tropomyosin Heterodimers.
Biochemistry,
51
(32).
pp. 6388-6399.
ISSN 0006-2960.
(doi:https://doi.org/10.1021/bi300340r)
(The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
(Contact us about this Publication)

Abstract

Tropomyosin (Tm) is a dimer made of two alpha helical chains associated into a parallel coiled-coil. In mammalian skeletal and cardiac muscle, the Tm is expressed from two separate genes to give the α- and β-Tm isoforms. These associate in vivo to form homo- (α2) and heterodimers (α·β) with little β2 normally observed. The proportion of α2 vs α·β varies across species and across muscle types from almost 100% α2- to 50% α·β-Tm. The ratio can also vary during development and in disease. The functional significance of the presence of these two isoforms has not been defined because it is difficult to isolate or purify the α·β dimer for functional studies. Here we report an effective method for purifying bacterially expressed Tm as α·β dimers using a cleavable N-terminal tag on one of the two chains. The same method can be used to isolate Tm dimers in which one chain carries a mutation. We go on to show that the α·β dimers differ in key properties (actin affinity, thermal stability) from either the α2- or β2-Tm. However, the ability to regulate myosin binding when combined with cardiac troponin appears unaffected.